Measurement of diffusion coefficients of meningococcal polysaccharide by optical mixing spectroscopy. I. A preliminary characterization on the aggregation of the Group C polysaccharide

The angular distribution of scattered intensity and decay times of concentration fluctuations have been measured by means of digital photon counting and single‐clipped photon correlation for solutions of Group C meningococcal polysaccharides at 31°C. The z‐average diffusion coefficient 〈D〉z and its second moment 〈D2〉z have been determined from the time‐dependent correlation function using the cumulant expansion technique. Very low observed values of 〈D〉z and the tremendous width of the polydispersity index, which is the z‐average normalized variance, suggest a higher degree of aggregation than the monomer–dimer type self‐association at finite concentrations.